The kinase activity of ATM is activated in response to DNA damage due to various stresses (e.g., UV irradiation, heat). Activated ATM then triggers following pathways leading to arrest in G1.

A. Chk2 is phosphorylated and, in turn, phosphorylates Cdc25A, thereby marking it for degradation and blocking its role in CDK2 activation.

B. Phosphorylation of p53 stabilizes it, permitting p53-activated expression of genes encoding proteins that cause arrest in G1, promote apoptosis, or participate in DNA repair.

C. Controlling the pool of p53, ATM phosphorylates MDM2 to inactivate it, causing increased stabilization of p53. Another protein p14ARF inhibits the activity of Mdm2 thus stabilizing p53.

Based on the above information, which one of the following statements is correct?

#Question id: 7221

#Unit 5. Developmental Biology

The cells of the neural plate are characterized by expression of the Sox family of transcription factors (Sox1, 2, and 3). These factors-

#Question id: 7222

#Unit 5. Developmental Biology

During development of sea urchin, The fates of the different cell layers are determined by which process?

#Question id: 7223

#Unit 5. Developmental Biology

In drosophila, the dorso-ventral axis of the embryo becomes divided into four regions early in embryogenesis.

A. The ventral mesoderm, which will form muscles and other internal connective tissues

B. The amnioserosa, which gives rise to an extra-embryonic membrane on the dorsal side of the embryo

C. The dorsal ectoderm, which gives rise to larval epidermis

D. The ventral ectoderm or neuroectoderm, which gives rise to the larval nervous system and epidermis

What is the correct sequence of these regions from ventral to dorsal?

#Question id: 7224

#Unit 5. Developmental Biology

Following statements are given regarding to the migration through primitive streak in chick.

A. Cells migrate to the primitive streak, and as they enter the embryo, the deep-moving cells give rise to the endodermal organs of the embryo, as well as to most of the extraembryonic membranes.

B. The migration of mesodermal cells through the anterior primitive streak and their condensation to form the chordamesoderm also appear to be controlled by FGF and Wnt signalling.

C. Wnt is expressed in the primitive streak and repels migrating cells away from the streak. 

D. Once cells migrate away from the streak, further movement of the mesodermal precursors appears to be regulated by FGF8 proteins.

Which of the following statement is incorrect?

#Question id: 7225

#Unit 5. Developmental Biology

The processes by which the three ectodermal regions are made physically and functionally distinct from one another is called neurulation. Following statements are regarding to the mechanism of neurulation.

A. The specification of the ectoderm is accomplished during gastrulation, primarily by regulating the levels of BMP experienced by the ectodermal cells.

B. High levels of BMP specify the cells to become neural plate.

C. Very low levels specify the cells to become epidermis.

D. Intermediate levels effect the formation of the neural crest cells.

Which of the following combination is correct?

#Question id: 7226

#Unit 5. Developmental Biology

Experimental evidences suggest that control of proximal-distal specification of the limb is correlated with the age of the progress zone mesenchyme. Match the following experiment (Column I) with their results (Column II).